Self-braking conveyer drive



Dec. 22, 1953 Filed Aug. 9, 1951 R. PETTERSON ET AL SELF-BRAKING CONVEYER DRIVE 2 Sheets-Sheet l INVENTORS REINHHRDT PETT'ERSON BlY ESL.lEVG\ WEYGFINDT TORNEYS Dec. 22, 1953 R. PETTl-:RsoN ET AL ASEI .F`BRAKING CONVEYER DRIVE 2 Sheets-Sheet 2 Filed Aug. 9, 1951 INVENTORS [1 REINHQRDT PETTERSON: LESLIE G.. WEYGQNDT BY W //ATTORNEYS Patented Dec. 22, 1953 lie G. Weygandt, Jenkintown, Ba., assignors to Hewitt-Robins incorporated, Buialo, N'. Y., a

corporation of New York Application August 9', 1951i, Serial Nd. 241,092

8' Claims.

This invention relates to conveyors and, al though its principles are not limited thereto, will be described and eXem-pliiied in relation to belt conveyors.

Its general object is to provide a solution for certain difficulties encountered in belt 4conveyor installations in which, by reason of the contour of the ground or other necessities of the situation, the load is to 'be conveyed over a path or under such conditions, that at some times the beltl instead of being driven tends to overrun its drive. A simple illustration is an installation in which there is high ground to be surmounted between the head and tail pulleys. At some times (as when starting up) the load or a major part of it will be moving upgrade, and at other times (for example, some time after the feed has been shut down) the load or a major part of it will be moving downgrade, that is toward the head pulley or drive. In this, as well as in morev complicated but analogous instances, the usual takeup in the return run of the belt functions normally, in the slack tension side of the belt, while the load is moving upgrade; but, when the load starts to move downgrade and overrun the drive, the return run of the belt, including the takeup becomes tensioned and the slack normally absorbed in the takeup tends to 'feed into the upper or load-carrying run of the belt, causing the latter to sag or whip. One Way tor overcome this diniculty is to overload the takeup, but the resulting tensioning of the 'belt requires that an extra heavy and hence costly belt be used.

More particularly, therefore, the object of the invention is to provide a conveyor drive which automatically overcomes the indicated difficulty and which does not require the use of extra heavy, costly belts or of additional drive motors.

In general, the invention comprises a drive so organized in relation to the takeup that the latter always operates in a slack tension stretch. of the belt or, otherwise stated, is never subjected` to tension created in the return run of the belt when the load is tending to overrun the drive.

The invention will be readily understood from the following description and accompanying" drawings in which:

Fig. l is a diagrammatic side elevation of a conveyor system incorporating an upgrade and a downgrade stretch and illustrating the general arrangement of head' drive pulleys and' takeup according to the invention;

Fig. 2 is an enlarged elevational View, also diagrammatic, of the drive' or head end of the sys* tem;

Fig. 3 is av View, on the line 3-3 of Fig. 2, schematically illustrating the drive coupling arrangement; and

Figs. 4 and 5 are broken-out elevations showing a preferred arrangement of clutch means under two different conditions of operation.

In the conveyor system schematically illus-'- trated in Fig. 1, the belt I is trained over `a tail pulley 2 and its upper run is assumed to travel from right to left, toward the motor-driven drive pulley 3 and to surmount a hump or elevation at some intermediate point. Somewhere in the return run of the belt there is ordinarily provided a takeup, herein illustrated conventionally at 4 adjacent the drive pulley 3', a takeup Weight being indicated at 5. On the outgoing or down stream vside of the talreup, the belt passes over a pulley t, whence it passes to the tail pulley 2,

When, in such an arrangement, the load or a major part oi it is on the upgrade stretch la of the belt, the system operates conventionally, with the upper run of the belt tensioned and the taleeup operating in the slacl; tension, return run. But when, for example, the feed to the belt at the tailend is shut down and the belt is advanced to apoint where most or all of the load is on the downgrade stretch lb, the pulley 3, normally motor-driven at constant speed, is overrun and driven 'by the descending belt load; and the tension created by the load in the stretch of the belt behind or' upstream of the load, tensions the norinally sla-ek return run, draws the belt' out of the takeup loop and passes it into the upper run which then sags or whips.

According to the present invention, means are provided which, und-er the load conditions last described (that is', when the load tends to overrun the drive pulley) automatically brakes pulle t so as to prevent the tension in the return run of the belt from being applied to the takeup. The latter is thereby permitted to function normally and` the feeding of surplus belt into thel upper of the v conveyor is avoided. For con venience, pulley t is referred to hereafter as the holdback pulley.

Referringv new to Figs. 2- and 3, a constant speed motor 8, through `a* suitable drive reduction Si, is coupled to drive a eountershaft lil` which is in turn coupled tothe shafts H1 and -2, respectively, of pulleys 3 and 6. However, the drives from the countersliai't to the respective pulleys incorpora-te suitable clutches and are so organized that under normal operating conditions (with the drive pulley functioning to haul the belt rather than being overrun oy it)` the cou- 3 pling to the holdback pulley is inoperative. The particular details of the clutches form no part of the invention and any type appropriate for the purpose may be used.

In this present illustrative embodiment, oneway clutches are incorporated in the pinions i3, i4 mounted on the countershaft I0, as indicated in Figs. 4 and 5, the pinions meshing with gears l5, I6 secured to the respective pulley shafts. For convenience, I3 will be referred to as the drive pinion and lLi as the holdback pinion and their respective clutches and gears by like designations. The clutches, being indicated as of conventional form, need not be described in detail. It will be apparent from Figs. 4 and 5 that when drive gear l tends to lag behind pinion I3, the motor-driven countershaft lil is clutched to and drives that pinion; and that when drive gear l overruns pinion i3 the drive clutch is thrown out. The oppositely arranged holdback clutch oi pinion ifi operates in similar fashion with respect to hold back gear I6.

Before describing the operation of the drive, one further feature may be noted and that is that to ensure engagement and disengagement of the respective clutches at appropriate times, the ratios of the drive connections or couplings het-Ween the motor and the respective pulleys are slightly different. This may be achieved by making the drive and holdback pulleys oi slightly diiferent diameter or, as is preferred, by incorporating a diierent number oi teeth in one or another of the pinions or gears. For present purposes it may be assumed that holdback pinion lli has one more tooth than drive pinion i3 with the result that the drive oi ie motor to the holdback pulley is through a slig tly higher gear ratio than the drive of the motor to the drive pulley.

The operation of the systen1^ will now he described, and iirst under what in this illustrative instance amounts to what will be termed normal conditions, that is, when the load or a major part of it is ascending the upgrade stretch.

The motor drives countershaft lil in the direction of the arrow (Fig. 4) and, through the drive clutch and pinion i3, the drive gear iai. Since the drive pulley and the holdbacl: pulley are induced to rotate at the same speed (by the belt) holdback gear i5 rotates at the saine speed as drive gear l5. But since the holdback pinion has one more tooth than the drive pinion, it rotates slower than the drive pinion. The net result is a relative vbackward movement of the holdback pinion ifi, that is, With respect to the countershaft and the holdback clutch is thereby moved to and maintained in its disengaged (Fig. Ll) position. In this situation, the takeup is, as usual, on the low or slack tension side of the drive pulley.

When now the condition changes so that the load or a major part of it is descending the downgrade stretch of the conveyor, the drive automatically accommodates itself to this new condition, as follows:

Both the drive pulley and the hoidback pulley, driven by the belt under the iniluence of the descending load, speed up or tend to overrun the motor; or in other words, the direction oi power transmission is no longer from the motor to the pulleys but from the pulleys to the motor. The countershaft ic, which is coupled to the motor, tends to maintain its former (motor) speed and, in the result, there is a relative backward movement of the countershaft with respect to the drive pinion and holdback pinion, both of which are now being driven, through the respective gears, at increased speed.

It will be seen (Fig. 5) that such relative nachn Ward movement of the countershaft causes the holdback clutch to engage and thus to transmit the drive from the now belt-driven lioldback pulley to the motor. It will also be seen that, due to the rotation of drive pinion i3 faster than holdback pinion Ell (because of the one tooth difference), .the drive pinion will be disengaged and held disengaged from the countershaft.

The motor is thus driven by the holdhack pulley and is speeded up to the point of functioning as a generator and exerting a braking eiect upon the holdback pulley, and when that cornes about it will be apparent that the lower run of the belt will be tensioned (under the influence of the downgrade load) back to but not beyond the holdhack pulley. In other words, referring to Fig. 2, the formerly slack tensioncd Zone il becomes tensioned and the formerly tensioned zone i8 becomes slack; while the formerly slack tenu sioned zones is and 2D continue slack.

Thus, no matter whether the drive pulley is operating under load, or is being overrun hy the load, the takeup continues to operate in a slack tension stretch of the belt and hence is not required to he overtensioned or overloaded to pre-- vent the belt in the takeup from being drawn out when the belt load is overrunning the drive pulley.

It will be understood that the location of the drive pulley is not coniined to what has been treated above as the head end of the conveyor; but, as in conveyor systems generally, can he located at the tail end or at an intermediate point in the return run of the 1eelt. 'Wherever located, the drive pulley and holdhacl pulley are located, as described, on opposite sides and respectively upstream and downstream with respect to the takeup.

It will also be understood that the invention is not limited to the details of the arrangement described and that its principles are susceptible to embodiment in various forms to meet the demands of particular installations.

In the light of the foregoing, the following is claimed:

l. In a conveyor drive, the combination of a drive pulley; a holdhacl; pulley on the down` stream side of the drive pulley; a talreup between the said pulleys; a 'eelt trained around the pulleys and through the intervening takeup; a constant-v speed drive motor; a drive connection between the motor and the drive pulley including a norn` mally engaged clutch adapted to disengage said connection when the drive pulley overruns the motor; a second drive connection between the holdbacl pulley and the motor including a nere mally disengaged clutch adapted to engage the said second drive connection when the holdbacl: pulley overruns the motor.

2. In a conveyor drive, the combination of a drive pulley; a holdback pulley on the downstream side of the drive pulle a talreup between the said pulleys; a belt trained around the pulleys and through the intervening takeup; a constantn speed drive motor; a one-way drive connection from the motor to the drive pulley; and a onea way drive connection from the holdback pulley to the motor.

3. In a conveyor drive, the combination of a drive pulley; a holdback pulley on the downstream side of the drive pulley; a takeup between the said pulleys; a belt trained around the pulleys and through the intervening takeup; a drive motor and couplings between the motor and each of the pulleys; and clutch means for simultaneously disengaging the coupling between the drive motor and the drive pulley and engaging the coupling between the holdback pulley7 and the motor, in response to driving of the drive pulley by the belt.

4. In a conveyor drive, the combination of a drive pulley; a holdback pulley on the downstream side of the drive pulley; a takeup between the said pulleys; a belt trained around the pulleys and through the intervening takeup; a drive motor and couplings between the motor and each of the pulleys; said couplings including oppositely arranged overrunning clutches and the drive of the motor-to-holdback-pulley coupling being of higher ratio than that of the motor-todrive pulley coupling.

5. In a conveyor drive, the combination of a drive pulley; a holdback pulley on the downstream side of the drive pulley; a takeup between the said pulleys; a belt trained around the pulleys and through the 'intervening takeup; a drive motor and couplings between the motor and each of the pulleys; said couplings including oneway clutches oppositely arranged, whereby when either one of said clutches is engaged the other is disengaged, the one-way clutch in the coupling between the motor and the drive pulley being arranged to transmit the normal drive from the motor to the drive pulley and the one-way clutch in the coupling between the motor and the holdback pulley being arranged to transmit power from the holdback pulley to the motor.

6. The combination with a conveyor belt, a drive pulley therefor and a takeup for the belt on 4the downstream side of the drive pulley, of: a holdback pulley engaged with the belt on the downstream side of the takeup; braking means; a normally inoperative connection between the braking means and the holdback pulley; and clutch means in said connection adapted to establish the said connection in response to driving of the drive pulley by the belt.

7. The combination with a conveyor belt, a drive pulley therefor and a takeup for the belt on the downstream side of the drive pulley, of a holdback pulley engaged with the belt on the downstream side of the takeup; holdback pulley braking means; and means whereby the braking means are rendered effective in response to predetermined belt speed.

8. In a conveyor drive, the combination of a drive pulley; a holdback pulley on the downstream side of the drive pulley; a takeup between the said pulleys; a belt trained around the pulleys and through the intervening takeup; and brake means for retarding the holdback pulley in response to the driving of the said pulleys by the belt at a predetermined speed above their normal operating speed.

REINHARDT PETTERSON. LESLIE G. WEYGANDT.

No references cited. 

